PROJECT SUMMARY/ABSTRACT While the scale of the HIV epidemic remains large, it has entered a promising new phase, marked by unprecedented progress and opportunities. In view of the need to rigorously test interventions to improve the uptake, implementation, and translation of recent scientific findings into standard of care (the know-do gap), as well as to evaluate the impact of bringing such interventions to scale, in 2014 we launched a research training program focused on Global HIV Implementation Science. Implementation science is the scientific study of methods to promote integration of research findings and evidence-based interventions into health care policy and practice, thus improving the quality and effectiveness of health services. A key element of translational research, implementation science encompasses a broad range of skills, including epidemiology, biostatistics, sociology, decision science, and health economics. The long-term objective of the Training Program is to prepare well-qualified individuals for careers as independently-funded researchers and for leadership in global HIV implementation research. We have assembled an outstanding group of diverse faculty from multiple schools, departments, and centers at Columbia University who have distinguished themselves in mentorship and are leading cutting edge implementation science research addressing HIV prevention among key populations, adolescents and young women; engaging adolescents and men in the care continuum; TB/HIV integration; and differentiated service delivery. The Training Program encompasses streamlined coursework based on an individualized training plan; weekly faculty-fellow seminars; tailored mentorship; research experience in a variety of domestic and international field settings; presentations; manuscript and grant preparation; research seminars and colloquia; and instruction in the responsible conduct of research. The Training Program also includes rigorous evaluation of the quality and effectiveness of the Training Program, to ensure that trainees achieve the competencies and skills necessary for success as future leaders in HIV implementation science research. The five-year program aims to support seven (five predoctoral and two postdoctoral) trainees at any one time. Among the postdoctoral trainees, a mix of trainees with PhD, DrPH, and MD degrees is sought. Predoctoral trainees are required to pursue a doctoral degree in Epidemiology. The period of support is three years for predoctoral candidates and two years for postdoctoral candidates. With stellar faculty, a unique training environment, and unparalleled research opportunities in domestic and international field settings, we are well- poised to continue to lead this novel effort and nurture new investigators trained in multidimensional, interdisciplinary approaches to advance scientific knowledge and demonstrate the impact of interventions.